Free fatty acid metabolism in fetal and newborn sheep

Abstract

The metabolism of free fatty acids (FFA) was studied in the term ewe, sheep fetus and newborn lamb. The concentration of FFA is about 10 times greater and the concentration of triglyceride fatty acids (TGFA) 2 1/2 times greater in maternal than in fetal plasma. After intravascular administration of palmitic acid-1-C14 complexed to homologous albumin, the initial rates of disappearance of FFA radioactivity from maternal and fetal circulations were similar, with half-times of approximately 2 minutes. Radioactivity appeared in the opposite circulation as FFA indicating that the syndesmochorial placenta is permeable to palmitic acid. Survival of the newborn lamb is associated with a fivefold increase in plasma concentration of FFA and no significant change in glucose or fructose during the first 30 minutes after birth. Failure to survive is associated with lack of increase in plasma FFA concentrations, while glucose concentrations do not differ from those found in surviving lambs. These data suggest that sympathetic nervous system activity is responsible for the FFA elevation and that increased activity of the sympathetic nervous system or FFA mobilization is closely related to survival of the newborn lamb.